Here’s what the research on the topic indicates:
Media Violence
John P Murray. The American Behavioral Scientist. Thousand Oaks: Apr 2008. Vol. 51, Iss. 8; pg. 1212
Abstract (Summary)
Fifty years of research on the effect of TV violence on children leads to the inescapable conclusion that viewing media violence is related to increases in aggressive attitudes, values, and behaviors. The changes in aggression are both short term and long term, and these changes may be mediated by neurological changes in the young viewer. The effects of media violence are both real and strong and are confirmed by the careful reviews of research evidence by various scientific and professional organizations that are concerned with children’s mental health and development. [PUBLICATION ABSTRACT]
Short-term and Long-term Effects of Violent Media on Aggression in Children and Adults
Brad J Bushman, L Rowell Huesmann. Archives of Pediatrics & Adolescent Medicine. Chicago: Apr 2006. Vol. 160, Iss. 4; pg. 348, 5 pgs
Abstract (Summary)
To test whether the results of the accumulated studies on media violence and aggressive behavior are consistent with the theories that have evolved to explain the effects. We tested for the existence of both short-term and long-term effects for aggressive behavior. We also tested the theory-driven hypothesis that short-term effects should be greater for adults and long-term effects should be greater for children. Meta-analysis. Children younger than 18 years and adults. Main Exposures: Violent media, including TV, movies, video games, music, and comic books. Measures of aggressive behavior, aggressive thoughts, angry feelings, physiological arousal (eg, heart rate, blood pressure), and helping behavior. Effect size estimates were combined using meta-analytic procedures. As expected, the short-term effects of violent media were greater for adults than for children whereas the long-term effects were greater for children than for adults. The results also showed that there were overall modest but significant effect sizes for exposure to media violence on aggressive behaviors, aggressive thoughts, angry feelings, arousal levels, and helping behavior. The results are consistent with the theory that short-term effects are mostly due to the priming of existing well-encoded scripts, schemas, or beliefs, which adults have had more time to encode. In contrast, long-term effects require the learning (encoding) of scripts, schemas, or beliefs. Children can encode new scripts, schemas, and beliefs via observational learning with less interference and effort than adults.